This invention relates generally to the sensing of electric charge in a relative sense and indicating quantitatively a change in potential for large bodies such as the earth which changes are related to various atmospheric and other natural phenomena. It is well known that a continuous fair weather atmospheric electric current condition exists with a vertical potential gradient from the earth to the upper atmosphere and that various properties of this electrical condition can be measured. For example, both the air-earth conduction current and the potential gradient are shown to exhibit a sunrise effect and these quantities exhibit a diurnal variation as well as annular and other variations. The apparatus used in such experiments, however, does not provide a means for indicating the charge on a body independent of a reference or quantatively detecting a change in that charge level independent of other references and, accordingly, the detection of this phenomenon and its correlation with natural phenomena has not heretofore been possible.